1. Field of the Invention
The present invention relates to a semiconductor device which is widely used regardless of the change in an operating voltage of a circuit element.
2. Description of Related Art
In general, a specification of a power supply voltage (or input voltage) is often changed in a semiconductor device (particularly, a semiconductor integrated circuit such as a microcomputer) without changing the function of semiconductor device. In this case, an operating voltage of the semiconductor device is, for example, obtained by using a voltage down circuit (VDC). That is, in cases where the power supply voltage is higher than the operating voltage of the semiconductor device, the power supply voltage is lowered to the operating voltage in the voltage down circuit, and the semiconductor device is operated by using electric power of the operating voltage obtained from the power supply voltage.
Therefore, even though the power supply voltage is higher than the operating voltage of the semiconductor device, it is not required to change a plurality of circuit elements composing the semiconductor device to ones suitable for the power supply voltage. As a result, a plurality of semiconductor devices having the same specification can be easily used in a semiconductor device field regardless of a difference in the power supply voltage.
FIG. 9A is a view showing the configuration of a conventional semiconductor device of a normal voltage type, and FIG. 9B is a view showing the configuration of a conventional semiconductor device of a low voltage type. In FIG. 9A and FIG. 9B, 11 indicates a substrate, 12 indicates a central processing unit (CPU), 13 indicates a timer, 14 indicates a voltage down circuit (VDC), and 15 indicates each of a plurality of input/output pads. The input/output pads 15 are arranged around a peripheral area of the substrate 11 so as to surround the CPU 12, the timer 13 and the VDC 14. Here, other peripheral functional circuits are omitted in FIG. 9A.
The conventional semiconductor device shown in FIG. 9A is used in cases where a power supply voltage is higher than an operating voltage of the CPU 12 and the timer 13 of the conventional semiconductor device, the power supply voltage is lowered to the operating voltage in the VDC 14, and electric power of the operating voltage obtained from the power supply voltage is supplied to the CPU 12 and the timer 13. This type of semiconductor device is called a normal voltage type semiconductor device in this specification.
In contrast, in cases where the power supply voltage is equal to an operating voltage of a conventional semiconductor device because the power supply voltage is low, as shown in FIG. 9B, the VDC 14 is removed from the conventional semiconductor device, and the power supply voltage is directly supplied to the CPU 12 and the timer 13 as the operating voltage. Therefore, the conventional semiconductor device shown in FIG. 9B is operated in the same manner as that of the conventional semiconductor device shown in FIG. 9A. This type of semiconductor device is called a low voltage type semiconductor device in this specification.
In cases where the normal voltage type semiconductor device is compared with the low voltage type semiconductor device, because of the difference in the existence of the VDC 14, a layout of a plurality of circuit elements (for example, the CPU 12 and the timer 13) surrounded by the input/output pads 15 in the normal voltage type semiconductor device inevitably differs from that in the low voltage type semiconductor device. Therefore, it is required to separately design both a layout of circuit elements in the normal voltage type semiconductor device and a layout of circuit elements in the low voltage type semiconductor device.
Because the conventional semiconductor devices have the above-described configurations respectively, even though a plurality of conventional semiconductor devices have the same specification, in cases where a plurality of operating voltages of the conventional semiconductor devices differ from each other, it is required to design a layout of circuit elements for each conventional semiconductor device. Therefore, in cases where a plurality of conventional semiconductor devices respectively operated at a plurality of operating voltages different from each other are used, even though the conventional semiconductor devices have the same specification, it is required to design a layout of circuit elements for each conventional semiconductor device. In this case, a problem has arisen that the conventional semiconductor devices having the same specification cannot be easily used in a semiconductor device field.
Also, in cases where electric power required in a conventional semiconductor device differs from that required in another conventional semiconductor device, even though a plurality of conventional semiconductor devices have the same specification, it is required to design a layout of circuit elements for each conventional semiconductor device. In this case, the same problem described above has arisen.
An object of the present invention is to provide, with due consideration to the drawbacks of the conventional semiconductor device, a semiconductor device which is easily used regardless of a change in an operating voltage or a required electric power.
The object is achieved by the provision of a semiconductor device which includes a circuit block having at least a circuit unit operated at a prescribed operating voltage, a voltage changing unit for changing a power supply voltage obtained from the outside to the prescribed operating voltage, and supplying means for supplying electric power of the prescribed operating voltage obtained by the voltage changing unit to the circuit unit of the circuit block. The voltage changing unit is arranged without making a connection with the circuit block.
Therefore, even though the circuit block operated at the prescribed operating voltage different from the power supply voltage is arranged in the semiconductor device, a layout of the circuit block can be fixed regardless of the operating voltage of the circuit block. Accordingly, a plurality of semiconductor devices can be widely used regardless of a difference in the operating voltages of the circuit blocks (or the circuit units).
The object is also achieved by the provision of a semiconductor device which includes a circuit block having a plurality of circuit units respectively operated at a plurality of operating voltages different from each other, a plurality of voltage changing units for changing a power supply voltage obtained from the outside to the operating voltages of the circuit units of the circuit block respectively, and supplying means for supplying the operating voltages obtained by the voltage changing units to the circuit units of the circuit block. The voltage changing units are arranged without making a connection with the circuit block.
Therefore, the circuit units operated at the operating voltages different from each other can be arranged in the semiconductor device. Accordingly, the semiconductor device can be flexibly used regardless of a difference in the operating voltages of the circuit units.
The object is also achieved by the provision of a semiconductor device which includes a circuit block having at least one circuit unit operated at a prescribed operating voltage, a plurality of voltage changing units for respectively changing a power supply voltage obtained from the outside to the prescribed operating voltage of the circuit unit of the circuit block, and supplying means for supplying electric power of the prescribed operating voltage of one voltage changing unit to the circuit unit of the circuit block and additionally supplying electric power of the prescribed operating voltage obtained by another voltage changing unit or the other voltage changing units to the circuit unit of the circuit block in a case where the electric power of the operating voltage is insufficient for the circuit unit of the circuit block. The voltage changing units are arranged without making a connection with the circuit block.
Therefore, the electric power of the operating voltage supplied to the circuit unit of the circuit block can be easily increased by adding a simple configuration of one voltage changing unit or more. Accordingly, a plurality of semiconductor devices can be widely used regardless of a difference in the electric power required in the circuit blocks (or the circuit units).